Tanzanite is a fascinating blue stone discovered fairly recently. A variety of zoisite with a very peculiar blue-violet colour, its discovery dates from January 1967 by a miner named Ndugu Jumanne Ngoma.
A fabulous story: on his way to visit his family, his attention is caught by very transparent and shiny crystals looking like rough tourmaline. A few hours later, the man has picked up from the ground several kilos of the stone, fascinated by the magnificent colour. He tries to sell it but at that time no one is interested. Eventually, the discovery is attributed to Manuel De Souza, who is the first to commercialise the stone one year later.
The gem’s value was recognised by the Maison Tiffany & Co in 1968, naming it tanzanite as a tribute to its country of origin. Close to the colour of the amethyst, the gem also has a bluish colour deep as sapphire. It may also appear pink, due to its natural and intense pleochroism which makes the stone fascinating. Moreover because it is found in only one place: at the foothills of the Kilimanjaro mountain. Extraction conditions are relatively difficult.
The colour of the stone is more or less intense according to the pavilion.
Tanzanite is a relatively fragile stone. It has a Mohs hardness of 6 to 6.5 (the Mohs scale goes from 1 (hardness of talc) to 10 (hardness of diamond). Tanzanite can be chipped. It has one direction of perfect cleavage, which makes it difficult to cut or set.
For these reasons it is recommended to pay particular attention to the gem and protect it, especially if it is set on a ring. When you decide to offer a tanzanite piece of jewellery, if it’s a ring, your jeweller will advise you to privilege the bezel or half-bezel setting. For earrings or pendants, the stone need less protection, a simple claw setting may suffice. If your tanzanite is eroded, it will cost a minimum of 90 € to repolish the facets, or 120 € to cut the stone. In all cases, request advice from your jeweller, who in turn will have direct advice from trustworthy gem-cutters.
This is why tanzanite is more often set on a pendant or earrings, as a new alternative to blue sapphire.
If you want to know more about the discovery and the history of the tanzanite, I recommend Valerio Zancanella‘s beautifully illustrated book, sold by the AFG (French Association of Gemmology).